Electronic components are in general subject to at least two stresses, an electrical stress, with increasing tendency to breakdown due to voltage, current or power and a thermal stress due to its own power dissipation and, in part, to the total dissipation of neighboring components and/or the local environment. Reducing electrical and thermal stress leads to products improved failure rates and extended useful life. This is a design aspect defined as component de-rating.
In most industries and in particular the Telecom industry this aspect is statically defined at the design phase of a product and is hard to change later on in the product life cycle since it does entitle a high cost both in terms of CAPEX and OPEX. To make sure the product meets its target worst case scenario operating conditions its components de-rating or stress reduction is usually targeted for the product maximum configuration and power load to avoid product operational degradation and failures for all the committed operating conditions ranges. For e.g. a shelf assembly having a battery of cooling air intake fans will have fan speed and volumetric capacity sized to accommodate worst-case power dissipation and environmental temperature conditions over which the total equipment is specified to operate.
However in most of the cases a significant portion of the equipment operates below the worst case conditions. Moreover the same given product can be targeted to different target useful life depending on the target market drivers (cost reductions, large variability in deployment sites environmental conditions, etc.). Hence designing the product with static de-rating limits without the ability to reduce or adjust the product cooling capabilities to meet dynamically changing useful life targets makes the product incur high design and deployment costs. For example a system designed to meet 20 years useful life for central office conditions with temperature range of −5 to +40 C cannot be adapted to run in extended temperature ranges say −40 C to +65 C by adjusting the system thermal flow to adjust the de-rating levels needed to meet 5 or 10 years useful life without the need to re-design or redeploy the product.
Further, though most of existing electronic systems thermal solutions work on preset cooling levels which can often be dynamically adjusted to air intake temperatures, they do not adapt per the internal system configuration or its electrical load changes which have to meet specific reliability targets. This results most of the time in inefficient system designs that drive overly high the cost of developing and operating such systems. Usually the amount of cooling delivered is engineered to allow a product quantified reliability and useful life target by designing the max components de-ratings.
Disadvantageously, provision of excess cooling capacity can result in significant wasted power, reduced product reliability and shortened useful life of fans, as well as high noise levels.